This present proposal is the competing continuation of the MBRS Program at the Medical Sciences Campus (Subprojects # 3, 4, 6, 9, 10, 18, 19 and 23). It is also a competing continuation proposal for eight (8) investigators of this Campus presently with the SUBE Program in the Rio Piedras Campus of this University. Eight new investigators have been incorporated into this application (1, 2, 5, 12, 13, 14, 15, and 24). Five of which have submitted proposals through a supplemental application that were approved but not funded in spite of the good score obtained. The present proposal is formed by 24 scientific projects and the administrative project. The subprojects can be tentatively arranged in various groups. One of these groups deals with cell biology (projects 1, 7, 8, 13, 18, 20, 22, and 23) and another one deals with immunology (projects 4, 12, 15, 17, and 24). The remaining subprojects are: hormones (project # 5 and 19), ethanol and other drugs (projects # 2, 3 and 14), kidney (projects # 11 and 21), Biochemistry (project # 9) and Natural Products (projects # 6 and 16). It is also worth mentioning that projects # 1, 3, 18 and 23 refer to the cell biology of vascular endothelial cells. The proposal requests 25 graduate and 28 undergraduate students for the first year of the grant. The number of graduate students increases to 29 in the subsequent years while the number of undergraduates remains about the same. A summer work program for five (5) medical and dental students is also requested. The total budget to carry out the program is $1,434,272 with $532,482,739 for personnel, $273,696 for equipment, 227,394 for supplies, and 372,380 for other expenses mostly for students).